Coating composition

ABSTRACT

A primer composition for application to a substrate to promote adhesion of a room-temperature-vulcanizable silicone rubber coating, comprises (A) an aminosilane material, (B) a chlorinated polyolefin and (C) a room-temperature-curable polydiorganosiloxane. The aminosilane material (A) is a primary amine-functional silane or the reaction product of a primary amine-functional silane with an epoxy-functional silane or an alpha, omega-dihydroxypolydimethylsiloxane oil.

FIELD OF THE INVENTION

This invention relates to a primer composition for application to asubstrate to promote adhesion of a room-temperature-vulcanisable (RTV)silicone rubber coating.

RTV silicone rubber coatings are applied to underwater surfaces, forexample ships' hulls, the cooling water inlets and outlets of powerstations, fish-farming equipment and the underwater and splash-zonesurfaces of oil production platforms, to inhibit fouling by aquaticorganisms such as algae and barnacles.

BACKGROUND OF THE INVENTION

Silicone rubber fouling-resistant coatings are described for example inGB-A-1307001, GB-A-1470465, GB-A-1581727, GB-A-2141436, EP-A-16195 andU.S. Pat. No. 3,702,778. RTV silicone rubber coatings have also beensuggested as coatings inhibiting the adhesion of ice, for example on thesuperstructure and topsides of ships.

A problem in the use of such RTV silicone rubber coatings is that it isdifficult to make them adhere well to substrates. This problem isdiscussed in EP-A-16195 which proposes applying the RTV silicone rubberas a cladding on a fabric backing.

Various primer compositions have been suggested forroom-temperature-vulcanisable silicone rubber antifoulings. U.S. Pat.No. 3,702,778 proposes a crosslinkable silicone paste. EP-A-89066proposes a mixture of an epoxysilane and a silane containing anunsaturated hydrocarbon group. JP-A-53-137231, JP-A-53-137233 andJP-A-53-137234 propose various elastomeric materials such aspolyurethane, natural rubber, chloroprene or neoprene rubber orbutyral/silicone rubber. EP-A-323906 and EP-A-329375 propose a siliconeresin containing an aminosilane.

U.S. Pat. No. 4,070,421 describes the use of chlorinated polyethylene asa primer for improving adhesion of coatings on polyolefin surfaces.

SUMMARY OF THE INVENTION

A primer composition according to the invention for application to asubstrate to promote adhesion of an RTV silicone rubber coatingcomprises:

(A) an aminosilane material which is

(i) a primary amine-functional silane of the formula:

    (RO).sub.x R.sub.(3-x) SiR.sup.1 NHR.sup.2                 (I)

where the radicals R, which can be the same or different, are monovalenthydrocarbon radicals having 1 to 12 carbon atoms and optionallycontaining an ether linkage; R¹ is an alkylene radical having 2 to 4carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbonatoms; R² is hydrogen or an alkylene radical of 2 to 4 carbon atomstipped with a primary amine group; and x is 2 or 3; or

(ii) the reaction product of a primary amine-functional silane of theformula (I) with an epoxy-functional silane of the formula:

    A--Si(B).sub.a (OB).sub.(3-a)                              (II)

where A is an epoxide-substituted monovalent hydrocarbon radical having4 to 12 carbon atoms; the radicals B, which can be the same ordifferent, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or1; or

(iii) the reaction product of a primary amine-functional silane of theformula (I) with an alpha, omega-dihydroxypolydimethylsiloxane oil ofthe formula:

    HO(Si(CH.sub.3).sub.2 O).sub.y H                           (III)

in which y is 2 to 60;

(B) a chlorinated polyolefin; and

(C) a room-temperature-curable polydiorganosiloxane.

DETAILED DISCLOSURE

In the primary amine-functional silane of formula (I) the radicals R arepreferably alkyl, for example methyl, ethyl, hexyl or octyl, aryl, forexample phenyl, or aralkyl, for example benzyl. The alkylene radical R¹is preferably --(CH₂)₃ --, --(CH₂)₄ -- or methyl-substitutedtrimethylene, or can be --(CH₂)₃ --O--(CH₂)₂, --(CH₂)₃ --O--(CH₂)₃ -- or--CH₂ --O--(CH₂)₂ --. R² is preferably hydrogen or --CH₂ CH₂ NH₂. It maybe preferred to separate any ether oxygen atom in R and R¹ by at leasttwo carbon atoms from the nearest heteroatom. Examples of primaryamine-functional silanes of formula (I) are: (CH₃ O)₃ Si(CH₂)₃ NH(CH₂)₂NH₂ ; (CH₃ CH₂ OCH₂ CH₂ O)₃ Si(CH₂)₂ NH₂ ; (C₂ H₅ O)₃ Si(CH₂)₃ NH₂ ;(CH₃ OCH₂ CH₂ O)₃ Si(CH.sub. 2)₃ NH₂ ; (C₂ H₅ O)₃ Si(CH₂)₃ O(CH₂)₃ NH₂ ;(C₂ H₅ O)₂ C₆ H₅ Si(CH₂)₃ NH₂ ; (C₂ H₅ O)₃ SiCH₂ O(CH₂)₂ NH₂ ; (C₂ H₅O)₃ Si(CH₂)₃ O(CH₂)₂ NH₂ ; and (C₂ H₅ O)₂ CH₃ Si(CH₂)₃ NH₂. Mixtures oftwo or more primary amine-functional silanes (I) may be used if desired.

The primary amine-functional silane (I) is preferably used as such inthe primer composition. It can however be replaced wholly or in part bya reaction product of the primary amine-functional silane (I) and anepoxy-functional silane (II). The group A in the epoxy-functional silane(II) is preferably a glycidoxy-substituted alkyl group, for example3-glycidoxypropyl. The epoxy-functional silane (II) can for example be3-glycidoxypropyl trimethoxy silane, 3-glycidoxypropyl diethoxy methoxysilane, 2-glycidoxypropyl trimethoxy silane,3-(3,4-epoxycyclohexyl)propyl trimethoxy silane or2-(3,4-epoxy-4-methylcyclohexyl)-ethyl trimethoxy silane. Examples ofpreferred reaction products of an amine-functional silane (I) and anepoxy-functional silane (II) are: ##STR1##

The aminosilane (I) and the epoxysilane (II) can be reacted at 20°-80°C., preferably using 0.4-1.2 primary amine groups of aminosilane (I) perepoxide group in (II).

In a further alternative, the primary amine-functional silane (I) isreplaced wholly or in part by a reaction product of the primaryamine-functional silane (I) and an alpha,omega-dihydroxypolydimethylsiloxane (III). (I) and (III) can be reactedat 20°-80° C., preferably using 0.4-1.2 alkoxy groups of aminosilane (I)per silanol group in (III).

The chlorinated polyolefin (B) preferably has a molecular weight of5,000 to 50,000 and a chlorine content of 15 to 75%, most preferably 17to 40%, by weight. Chlorinated polyolefins are commercially available.They can be prepared by treating a polyolefin with chlorine in thepresence of a peroxide catalyst. The chlorination reaction is preferablycarried out in a solvent for the polyolefin starting material. Thepolyolefin is preferably a poly(alpha-olefin) such as polyethylene orpolypropylene. The polyolefin can be of high or low density, amorphousor crystalline. It can be a copolymer of two or more olefins, preferablyalpha-olefins. Suitable chlorinated polyolefins are described forexample in U.S. Pat. No. 3,561,965 and U.S. Pat. No. 4,070,421.

The chlorinated polyolefin (B) can be used in conjunction with anotherchlorinated hydrocarbon resin, for example a chlorinated polyterpeneresin or chlorinated polystyrene. The polystyrene is preferably of lowmolecular weight (less than 5000). Such a chlorinated hydrocarbon resinpreferably has a similar degree of chlorination to the chlorinatedpolyolefin. The chlorinated hydrocarbon resin can for example be used inan amount of from 1 to 100% by weight based on the chlorinatedpolyolefin (B).

The aminosilane material (A) is generally used at 0.1 to 50% by weightbased on the chlorinated material (chlorinated polyolefin (B) plus anyother chlorinated hydrocarbon resin), most preferably 1 to 20% byweight.

The room-temperature-curable polydiorganosiloxane (C) is preferably apolydiorganosiloxane of viscosity 700 to 1,000,000 m Pa s at 25° C. Itpreferably contains silicon-bonded hydroxyl groups, for example analpha, omega-dihydroxypolydiorganosiloxane, or silicon-bondedhydrolysable groups, for example a polydiorganosiloxane tipped withsilicon-bonded hydrolysable groups. More preferably, it is formed ofrecurring diorganosiloxy units of the formula --R⁴ ₂ SiO-- where theradicals R⁴, which can be the same or different, represent hydrocarbonradicals having 1 to 10 carbon atoms. It is preferred that at least 50%of the radicals R⁴ are methyl groups. The dihydroxypolydiorganosiloxanemay further contain monoorganosiloxy groups of the formula R⁴ SiO₁.5and/or siloxy groups of the formula SiO₂ in a maximum proportion of 2%with respect to the number of diorganosiloxy groups R⁴ ₂ SiO.

The hydrocarbon radicals represented by the symbol R⁴ in the di- andmono-organosiloxy units may suitably be selected from alkyl radicalssuch as methyl, ethyl, n-propyl, isopropyl, n-butyl, n-pentyl, n-hexyl,2-ethyl hexyl or n-octyl, cycloalkyl radicals having from 4 to 8 carbonatoms such as cyclopentyl, cyclohexyl or methylcyclohexyl, alkenylradicals having from 2 to 4 carbon atoms such as vinyl, allyl orbuten-2-yl, and aryl radicals having from 6 to 8 carbon atoms such asphenyl, tolyl or xylyl.

As preferred examples of the groups represented by R⁴ ₂ SiO thefollowing formulae are noted: ##STR2##

One example of a suitable alpha, omega-dihydroxy polydimethylsiloxane isthat sold by Rhone Poulenc under the trade name "48V 3500".

Alpha, omega-dihydroxypolydiorganosiloxanes can readily be prepared bywell-known techniques described, for example, in FR-A-1134005,FR-A-1198749 and FR-A-1226745. The polydiorganosiloxanes are preferablyseparated from volatile by-products before use, for example by thedevolatilisation process described in U.S. Pat. No. 4,356,116.

Preferred alpha, omega-dihydroxypolydimethylsiloxanes consist ofsuccessive groups of the formula (CH₃)₂ SiO or contain up to 10%, forexample 2-10%, by mole of their groups R⁴ as phenyl groups, for examplein the form of (C₆ H₅)₂ SiO units.

Alpha, omega-dihydroxypolydiorganosiloxanes are generally used with acuring agent, for example a compound containing at least twosilicon-bonded hydrolysable groups per molecule. Examples of suitablecuring agents are ketiminoxysilanes, acyloxysilanes and alkoxysilanes,tetraalkyl titanates and aluminium alcoholates.

A ketiminoxysilane curing agent preferably contains at least twosilicon-bonded hydrolysable ketiminoxy groups per molecule. Such acuring agent is preferably used at 1 to 18 parts by weight per 100 partsof alpha,omega-dihydroxypolydiorganosiloxane. The ketiminoxysilanecuring agent may have the general formula:

    Y.sup.1.sub.f SiZ.sup.1.sub.(4-f)

in which:

Y¹ represents a hydrocarbon radical having 1 to 10 carbon atoms, whichmay be substituted by halogen or cyano;

Z¹ represents a hydrolysable radical of the formula:

    (Z.sup.2).sub.2 C=NO--

or ##STR3## in which the groups Z², which can be the same or different,represent C₁ -C₈ hydrocarbon radicals and E¹ represents a C₄ -C₈alkylene radical; the groups Z¹ can be the same or different; and

f represents 0 or 1.

Examples of group Y¹ are those listed above as examples of group R⁴ inthe diorganosiloxy units.

Examples of ketiminoxysilane curing agents are those of the formulae:##STR4## Si[ON=C(C₂ H₅)(CH₃)]₄ or Si[ON=C(CH₃)₂ ]₄ and their mixtures.

An acyloxysilane curing agent can for example have the formula:

    R.sup.5.sub.a Si(OCOR.sup.6).sub.4-a,

where R⁵ is defined as for group R⁴ mentioned above, R⁶ is a monovalenthydrocarbon radical, e.g. of up to 8 carbon atoms, without aliphaticunsaturation and a is 0 or 1. The radicals R⁶ can for example be alkylsuch as methyl, ethyl, n-propyl, n-butyl or n-hexyl, cycloalkyl such ascyclopentyl or cyclohexyl, or aryl such as phenyl, tolyl or xylyl.Examples of acyloxysilane curing agents are: ##STR5##

An acyloxysilane curing agent can for example be used at 2-20% by weightbased on the alpha, omega-dihydroxypolydiorganosiloxane.

An alkoxysilane curing agent can for example be a tetraalkylorthosilicate (tetraalkoxysilane) such as tetraethyl orthosilicate or analkyl trialkoxysilane such as methyl trimethoxysilane, ethyltrimethoxysilane or methyl triethoxysilane. Alkoxysilane curing agentssuch as tetraethyl orthosilicate are particularly preferred for use withmoisture-curable polydiorganosiloxanes.

The room-temperature-curable polydiorganosiloxane (C) can bemoisture-curable because atmospheric moisture is usually present whencoating a marine surface. A moisture-curable polydiorganosiloxane canfor example have hydrolysable end groups. The polydiorganosiloxane (C)containing silicon-bonded hydrolysable groups is preferably formed bycombining an alpha,omega-dihydroxypolydiorganosiloxane with a compoundcontaining at least two silicon-bonded hydrolysable groups per molecule.Examples of suitable compounds of this type are the ketiminoxysilanesand acyloxysilanes described above as curing agents, for example methyltriacetoxy silane, which form polydiorganosiloxanes tipped withsilicon-bonded hydrolysable ketiminoxy or acyloxy groups. Reactionbetween the silicon-bonded hydroxyl groups of thealpha,omega-dihydroxypolydiorganosiloxane and the silicon-bondedhydrolysable groups of the said compound generally takes place as thesematerials are combined, so that the polydiorganosiloxane (C) is at leastpartially tipped with silicon-bonded hydroxyl groups.

An alternative polydiorganosiloxane (C) tipped with silicon-bondedhydrolysable groups is an amine-tipped polydiorganosiloxane, for examplean alpha,omega-diaminopolydiorganosiloxane of the formula: ##STR6##where R⁴ is defined as above, n is an integer such that thepolydiorganosiloxane has a viscosity of 700-1,000,000 m Pa s at 25° C.,and R⁷ and R⁸ each represent hydrogen or a monovalent hydrocarbon grouphaving 1 to 10 carbon atoms. Most preferably R⁷ represents hydrogen andR⁸ represents an alkyl group having 2 to 6 carbon atoms, for exampleethyl, propyl, isopropyl, n-butyl or sec-butyl (but-2-yl). Examples ofamine-tipped polydiorganosiloxanes are sold under the Trade Marks"Silgan 500" and "Silgan 501J".

The room-temperature-curable polydiorganosiloxane (C) is preferably usedat 0.1 to 100 parts by weight, more preferably 1 to 50 parts by weight,per part by weight of the chlorinated material (chlorinated polyolefin(B) plus any other chlorinated hydrocarbon resin).

The primer composition may contain a catalyst for the room-temperaturecuring of the polydiorganosiloxane. Examples of catalysts are metallicand organometallic salts of carboxylic acids. Metallic salts may besalts of tin, lead, nickel, cobalt, iron, chromium, zinc or manganese,for example stannous octoate. Preferred organometallic salts arediorganotin carboxylate compounds such as dibutyltin dilaurate ordibutyltin acetate. Organic titanium derivatives containing at least one--Ti--O--Si-- or --Ti--O--C-- linkage, e.g. an alkanolamine titanate,and organic zirconium derivatives can be used as catalyst, as describedin U.S. Pat. No. 4,525,565.

The primer compositions preferably contain an organic diluent which canfor example be an aliphatic, cycloaliphatic or aromatic hydrocarbonwhich is optionally halogenated such as n-heptane, n-octane,cyclohexane, methylcyclohexane, toluene, xylene, mesitylene, cumene,tetrahydronaphthalene, perchloroethylene, trichloroethane,tetrachloroethane, chlorobenzene or orthodichlorobenzene, an aliphaticor cycloaliphatic ketone such as methylethylketone,methylisobutylketone, methylisoamylketone, cyclohexanone or isophorone;an ether such as a dialkyl ether of ethylene glycol or propylene glycol,or an ester such as ethyl acetate, butyl acetate or ethoxyethyl acetate.The diluent is preferably a solvent for the chlorinated polyolefin (B),including any other chlorinated hydrocarbon resin present. The weightratio of diluent to chlorinated polyolefin plus any other chlorinatedhydrocarbon resin is preferably in the range 1:3 to 20:1, morepreferably 2:3 to 10:1. The weight ratio of diluent toroom-temperature-curable polydiorganosiloxane is usually 1:50 to 20:1,preferably 1:10 to 3:1.

The primer composition can be prepared by mixing the aminosilanematerial (A) and the chlorinated polyolefin (B) with theroom-temperature-curable polydiorganosiloxane (C). The chlorinatedpolyolefin (B) and any other chlorinated hydrocarbon resin present arepreferably dissolved in an organic solvent before mixing with theaminosilane material (A) and the polydiorganosiloxane (C).

The primer composition can also contain additives selected frompigments, mineral fillers, thixotropic agents, stabilisers, surfactants,antioxidants and plasticisers. It may be preferred to include colouringpigments in the primer composition so that it can be overcoated by afouling-resistant layer of clear RTV silicone rubber. When incorporatingpigments, it may be necessary to take precautionary steps to avoid anymoisture present in the pigment from instigating premature curing of theroom-temperature-curable polydiorganosiloxane (C). The simplestprecaution is to ensure that any pigments used are thoroughly dry.Alternatively, the pigments can be dispersed in a diluent, preferably apolydiorganosiloxane, which inhibits reaction of any moisture present inthe pigment with the room-temperature-curable polydiorganosiloxane (C).The pigment can for example be dispersed in a non-reactivepolydiorganosiloxane oil such as a methyl-tipped polydimethylsiloxaneoil before the pigment contacts the room-temperature-curablepolydiorganosiloxane (C) (including any curing agent therefor) andpreferably also before the pigment contacts the aminosilane material(A). In an alternative procedure the pigment is dispersed in a liquidhydroxyl-tipped polydiorganosiloxane before the pigment contacts theaminosilane material (A) or any curing agent or material containingsilicon-bonded hydrolysable groups which forms part of theroom-temperature-curable polydiorganosiloxane (C). When this alternativeprocedure is used, the liquid hydroxyl-tipped polydiorganosiloxane usedas dispersion medium will generally become co-cured with theroom-temperature-curable polydiorganosiloxane (C). It can itself be usedas the room-temperature-curable polydiorganosiloxane (C), in conjunctionwith a curing agent added later. It is generally preferred however thata liquid hydroxyl-tipped polydiorganosiloxane used as dispersion mediumfor the pigment forms only part of the polydiorganosiloxane (C); forexample it can be used with a later-added moisture-curablepolydiorganosiloxane (C) tipped with hydrolysable groups.

The primer composition is particularly effective in promoting adhesionto organic resin substrates such as neoprene rubber, chlorinated rubber,block copolymer rubbers such as polystyrene/polybutadiene orpolystyrene/poly(ethylene-butylene) rubbers, polyurethanes, (bothelastomers and thermoplastic resins), epoxy coatings, vinyl resins suchas vinyl chloride polymers or alkyd resins. These resins may for examplebe in the form of cladding in the case of neoprene and similar rubbers,or may be previously-applied coatings, for example anticorrosivecoatings which are to be covered by a silicone rubber antifouling paint,or old antifouling coatings which are to be overcoated. The primercomposition also promotes adhesion to metal substrates such as aluminiumor steel.

The primer composition can be applied to the substrate by any knowncoating technique. Usually it is applied by spray, brush or roller.

The RTV silicone rubber fouling-resistant coating which is applied overthe primer composition can for example be based on an alpha,omega-dihydroxypolydiorganosiloxane as described above, used with acuring agent selected from those described above and optionally acatalyst selected from those described above. Alternatively, the RTVsilicone rubber can be a polydiorganosiloxane tipped with silicon-bondedhydrolysable groups as described above, for example silicon-bondedketiminoxy or acyloxy groups. It may be preferred that the curing agentor silicon-bonded hydrolysable groups in the room-temperature-curablediorganopolysiloxane (C) in the primer composition and the curing agentor silicon-bonded hydrolysable groups in the RTV silicone rubber coatingare the same. The RTV silicone rubber coating preferably includes anon-reactive silicone oil, for example of the formula: Q₃ Si--O--(SiQ₂--O--)_(n) SiQ₃, wherein each group Q represents a hydrocarbon radicalhaving 1-10 carbon atoms and n is an integer such that the silicone oilhas a viscosity of 20 to 5000 m Pa s. At least 10% of the groups Q aregenerally methyl groups and at least 2% of the groups Q are preferablyphenyl groups. Most preferably, at least 25% of the --SiQ₂ --O-- unitsare methylphenylsiloxane units. Most preferably the non-reactivesilicone oil is a methyl-terminated poly(methylphenylsiloxane). The oilpreferably has a viscosity of 20 to 1000 m Pa s and is preferably usedat 1 to 50%, most preferably 2 to 20%, by weight based on the RTVsilicone rubber. An example of a preferred non-reactive silicone oil isthat sold under the Trade Mark "Rhodorsil Huile 550". The non-reactivesilicone oil improves the resistance of the composition to aquaticfouling.

Instead of, or in addition to, the non-reactive silicone oil, the RTVsilicone rubber composition can contain a non-reactive fluid organichydrocarbon, for example a lubricating mineral oil such as white oil, alow molecular weight polybutene or petrolatum or a liquidparaffin/petrolatum mixture. Such a non-reactive fluid organichydrocarbon is preferably absent from the primer composition.

The primer composition improves the overall adhesion of the RTV siliconerubber to the substrate to a greater extent than can be achieved in theabsence of any of the essential components (A), (B) and (C). Theaminosilane material (A) and chlorinated polyolefin (B) ensure strongadhesion of the primer to the RTV silicone rubber and to the organicresin substrate respectively. We have however found that when acomposition comprising aminosilane material (A), chlorinated polyolefin(B) and solvent is applied to many organic resin substrates it israpidly absorbed by the substrate, so that adhesion of a subsequentlyapplied RTV silicone rubber coating is poor unless it is applied verysoon. The room-temperature-curable polydiorganosiloxane (C) counteractsthe tendency for the primer composition to be absorbed by the substrate,allowing a much longer time period, for example up to a week or evenlonger, within which overcoating with an RTV silicone rubber compositioncan be achieved with good adhesion.

The primer composition according to the invention has much greateradhesion to many substrates, in particular neoprene, chloroprene orhydrocarbon rubbers, than a composition which does not containchlorinated polyolefin. On all substrates, including those such as epoxyresin where the simple combination of room-temperature-curablepolydiorganosiloxane and aminosilane material gives good adhesion, thechlorinated polyolefin improves the resistance to sea water immersion;good adhesion of the primer composition to the substrate and of the RTVsilicone rubber top coat to the primer composition is maintained evenafter 18 months or more of immersion in sea water.

The invention is illustrated by the following Examples in which partsand percentages are by weight.

EXAMPLE 1

25 parts of a 40% solution in xylene of a chlorinated polyethylene(chlorine content 22%) was mixed with 2 partsN-(2-aminoethyl)-3-aminopropyl trimethoxy silane and diluted with 73parts xylene.

14 parts of the resulting composition was mixed with 61 parts of aroom-temperature-curable polydiorganosiloxane composition and 25 partsmethyl isoamyl ketone solvent. The room-temperature-curablepolydiorganosiloxane composition comprised an alpha,omega-dihydroxypolydimethylsiloxane used with a ketiminoxysilane curingagent.

The resulting primer composition was applied to a neoprene rubbersubstrate, and also to substrates coated with epoxy resin, polyurethane,vinyl resin and alkyd resin anticorrosive paints, and to a substratehaving the residue of an old antifouling paint based on rosin, a vinylchloride copolymer and cuprous oxide. In all cases the coating of primercomposition could be overcoated with an RTV silicone rubberfouling-resistant composition based on an alpha,omega-dihydroxypolydiorganosiloxane with a ketiminoxysilane curing agentand a non-reactive poly(methyl phenyl siloxane) oil about 10 minutesafter application of the primer composition with good adhesion of theRTV composition, and could also be overcoated with the RTV composition24 hours later with good adhesion.

The overcoated materials were immersed in sea water. Adhesion betweenthe primer composition and the substrates, and between the RTV siliconerubber fouling-resistant coating and the primer composition, remainedstrong after 18 months immersion in sea water.

EXAMPLE 2

29.7 parts of pigments and fillears (barytes, titanium dioxide, fumedsilica and black iron oxide) and 0.1 part of dibutyltin dilaurate curingcatalyst were dispersed by milling in 6.7 parts of non-reactivemethyl-tipped polydimethylsiloxane oil and 10.6 parts of methyl isoamylketone solvent. The resulting pigment dispersion was mixed with 36.4parts of room-temperature-curable polydimethylsiloxane tipped withketiminoxy groups, 8.3 parts of the solution of chlorinated polyethyleneand N-(2-aminoethyl)-3-aminopropyl trimethoxy silane described inExample 1 and 8.2 parts of methyl isoamyl ketone.

The resulting primer composition was applied to epoxy resin, neoprenerubber and urethane rubber substrates. These samples were overcoatedafter 16 to 48 hours with the RTV silicone rubber of Example 1.

The overcoated materials were immersed in sea water. Adhesion betweenthe primer composition and the substrates, and between the RTV siliconerubber fouling-resistant coating and the primer composition, remainedstrong after 16 months' immersion in sea water.

EXAMPLE 3

28.1 parts of pigments and fillers (titanium dioxide, barytes, blackiron oxide and fumed silica) were dispersed by milling in 11.5 parts ofliquid hydroxyl-tipped polydimethylsiloxane with 0.5 part of wetting aidand 11.4 parts of methyl isoamyl ketone. The resulting pigmentdispersion was mixed with 7.6 parts of the solution of chlorinatedpolyethylene and N-(2-aminoethyl)-3-aminopropyl trimethoxy silanedescribed in Example 1, 30.9 parts of room-temperature-curablepolydimethylsiloxane tipped with ketiminoxy groups, 0.03 part ofdibutyltin dilaurate and 10.0 parts of methyl isoamyl ketone.

The resulting primer composition was applied to substrates of epoxyresin, aluminium, urethane rubber, neoprene rubber, a substrate having aresidue of old antifouling paint as described in Example 1,polystyrene/polybutadiene block copolymer rubber andpolystyrene/poly(ethylene-butylene) block copolymer rubber. Thesesamples were overcoated after 16 to 48 hours with the RTV siliconerubber of Example 1.

The overcoated materials were immersed in sea water. Adhesion betweenthe primer composition and the substrates, and between the RTV siliconerubber fouling-resistant coating and the primer composition, remainedstrong after 6 months' immersion in sea water.

We claim:
 1. A primer composition for application to a substrate topromote adhesion of a room-temperature-vulcanisable silicone rubbercoating, which primer composition comprises:(A) an amino-substitutedsilicon compound which is selected from the group consisting of:(i)primary amine-functional silanes of the formula:

    (RO).sub.x R.sub.(3-x) SiR.sup.1 NHR.sup.2                 (I)

where the radicals R, which can be the same or different, are monovalenthydrocarbon radicals having 1 to 12 carbon atoms and optionallycontaining an ether linkage; R¹ is an alkylene radical having 2 to 4carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbonatoms; R² is hydrogen or a (primary amino)-alkyl group having 2 to 4carbon atoms; and x is 2 or 3; (ii) reaction products of a primaryamine-functional silane of the formula (I) with an epoxy-functionalsilane of the formula:

    A-- Si(B).sub.a (OB).sub.(3-a)                             (II)

where A is an epoxide-substituted monovalent hydrocarbon radical having4 to 12 carbon atoms; the radicals B, which can be the same ordifferent, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or1; and (iii) reaction products of a primary amine-functional silane ofthe formula (I) with an alpha, omega-dihydroxypolydimethylsiloxane oilof formula:

    HO(Si(CH.sub.3).sub.2 O).sub.y H                           (III)

in which y is 2 to 60; (B) a chlorinated polyolefin; and (C) apolydiorganosiloxane composition which is self-curable ormoisture-curable at ambient temperature.
 2. A primer compositionaccording to claim 1, wherein the polydiorganosiloxane composition (C)comprises an alpha, omega-dihydroxypolydiorganosiloxane and aketiminoxysilane curing agent.
 3. A primer composition according toclaim 1, wherein the polydiorganosiloxane composition (C) comprises analpha, omega-dihydroxypolydiorganosiloxane and an acyloxysilane curingagent.
 4. A primer composition according to claim 1, wherein thepolydiorganosiloxane composition (C) comprises an alpha,omega-dihydroxypolydiorganosiloxane and an alkoxysilane curing agent. 5.A primer composition according to claim 1, wherein thepolydiorganosiloxane composition (C) comprises a polydiorganosiloxanecontaining silicon-bonded hydrolysable groups as terminal groups.
 6. Aprimer composition according to claim 5, wherein the silicon-bondedhydrolysable groups are ketiminoxy, acyloxy or amine groups.
 7. A primercomposition according to claim 1 wherein the chlorinated polyolefin (B)has a chlorine content of 17 to 40% by weight.
 8. A primer compositionaccording to claim 1, wherein the composition contains anotherchlorinated hydrocarbon resin in addition to the chlorinated polyolefin(B), said another chlorinated hydrocarbon resin being present in anamount of 1 to 100% by weight based on the chlorinated polyolefin (B).9. A primer composition according to claim 1, wherein the aminosilanematerial (A) is present in an amount of 1 to 20% by weight based on theweight of chlorinated polyolefin (B) present in the composition.
 10. Aprimer composition according to claim 1, wherein the weight ratio of thepolydiorganosiloxane composition (C) to the chlorinated polyolefin (B)present in the composition is 1:1 to 50:1.
 11. A primer compositionaccording to claim 1, wherein a pigment is dispersed in the composition.12. A primer composition according to claim 8, wherein the aminosilanematerial (A) is present in an amount of 1 to 20% by weight based on theweight of chlorinated polyolefin (B) plus any other chlorinatedhydrocarbon resin present in the composition.
 13. A primer compositionaccording to claim 8, wherein the weight ratio of thepolydiorganosiloxane composition (C) to the chlorinated polyolefin (B)plus any other chlorinated hydrocarbon resin present in the compositionis 1:1 to 50:1.
 14. A process for preparing a pigmented primercomposition comprising dispersing a pigment in a non-reactivepolydiorganosiloxane oil and mixing the resulting pigment dispersionwith:(A) an amino-substituted silicon compound which is selected fromthe group consisting of(i) primary amine-functional silanes of theformula:

    (RO).sub.x R.sub.(3-x) SiR.sup.1 NHR.sup.2                 (I)

where the radicals R, which can be the same or different, are monovalenthydrocarbon radicals having 1 to 12 carbon atoms and optionallycontaining an ether linkage; R¹ is an alkylene radical having 2 to 4carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbonatoms; R² is hydrogen or a (primary amino)-alkyl group having 2 to 4carbon atoms; and x is 2 or 3; (ii) reaction products of a primaryamine-functional silane of the formula (I) with an epoxy-functionalsilane of the formula:

    A-- Si(B).sub.a (OB).sub.(3-a)                             (II)

where A is an epoxide-substituted monovalent hydrocarbon radical having4 to 12 carbon atoms; the radicals B, which can be the same ordifferent, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or1; and (iii) reaction products of a primary amine-functional silane ofthe formula (I) with an alpha, omega-dihydroxypolydimethylsiloxane oilof formula:

    HO(Si(CH.sub.3).sub.2 O).sub.y H                           (III)

in which y is 2 to 60; (B) a chlorinated polyolefin; and (C) apolydiorganosiloxane composition which is self-curable ormoisture-curable at ambient temperature,said step of dispersing thepigment in a non-reactive polydiorganosiloxane oil being carried outbefore the pigment contacts the amino-substituted silicon compound (A)or the polydiorganosiloxane composition (C).
 15. A process for preparinga pigmented primer composition comprising dispersing a pigment in aliquid hydroxyl-terminated polydiorganosiloxane and mixing the resultingpigment dispersion with(A) an amino-substituted silicon compound whichis selected from the group consisting of(i) primary amine-functionalsilanes of the formula:

    (RO).sub.x R.sub.(3-x) SiR.sup.1 NHR.sup.2                 (I)

where the radicals R, which can be the same or different, are monovalenthydrocarbon radicals having 1 to 12 carbon atoms and optionallycontaining an ether linkage; R¹ is an alkylene radical having 2 to 4carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbonatoms; R² is hydrogen or a (primary amino)-alkyl group having 2 to 4carbon atoms and x is 2 or 3; (ii) reaction products of a primaryamine-functional silane of the formula (I) with an epoxy-functionalsilane of the formula:

    A-- Si(B).sub.a (OB).sub.(3-a)                             (II)

where A is an epoxide-substituted monovalent hydrocarbon radical having4 to 12 carbon atoms; the radicals B, which can be the same ordifferent, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or1; and (iii) the reaction products of a primary amine-functional silaneof the formula (I) with an alpha, omega-dihydroxypolydimethylsiloxaneoil of the formula:

    HO(Si(CH.sub.3).sub.2 O).sub.y H                           (III)

in which y is 2 to 60; (B) a chlorinated polyolefin; and (C) apolydiorganosiloxane composition which is self-curable ormoisture-curable at ambient temperature,said step of dispersing thepigment in a liquid hydroxyl-terminated polydiorganosiloxane beingcarried out before the pigment contacts the amino-substituted siliconcompound (A) or any curing agent or material containing silicon-bondedhydrolysable groups which forms part of the polydiorganosiloxane (C).16. A process for preparing a pigmented primer composition comprisingdispersing a pigment in a liquid hydroxyl-terminatedpolydiorganosiloxane and mixing the resulting pigment dispersion with(A)an amino-substituted silicon compound which is selected from the groupconsisting of(i) primary amine-functional silanes of the formula:

    (RO).sub.x R.sub.(3-x) SiR.sup.1 NHR.sup.2                 (I)

where the radicals R, which can be the same or different, are monovalenthydrocarbon radicals having 1 to 12 carbon atoms and optionallycontaining an ether linkage; R¹ is an alkylene radical having 2 to 4carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbonatoms; R² is hydrogen or a (primary amino)-alkyl group having 2 to 4carbon atoms and x is 2 or 3; (ii) reaction products of a primaryamine-functional silane of the formula (I) with an epoxy-functionalsilane of the formula:

    A-- Si(B).sub.a (OB).sub.(3-a)                             (II)

where A is an epoxide-substituted monovalent hydrocarbon radical having4 to 12 carbon atoms; the radicals B, which can be the same ordifferent, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or1; and (iii) reaction products of a primary amine-functional silane ofthe formula (I) with an alpha, omega-dihydroxypolydimethylsiloxane oilof the formula:

    HO(Si(CH.sub.3).sub.2 O).sub.y H                           (III)

in which y is 2 to 60; (B) a chlorinated polyolefin; and (C) a curingagent which together with the liquid hydroxyl-terminatedpolydiorganosiloxane forms the room-temperature-curablepolydiorganosiloxane (C),said step of dispersing the pigment in a liquidhydroxyl-terminated polydiorganosiloxane being carried out before thepigment contacts the amino-substituted silicon compound (A) or the saidcuring agent.
 17. A process for coating a substrate with aroom-temperature-vulcanisable silicone rubber composition, wherein thesubstrate is coated with a primer composition which comprises:(A) anamino-substituted silicon compound which is selected from the groupconsisting of(i) primary amine-functional silanes of the formula:

    (RO).sub.x R.sub.(3-x) SiR.sup.1 NHR.sup.2                 (I)

where the radicals R, which can be the same or different, are monovalenthydrocarbon radicals having 1 to 12 carbon atoms and optionallycontaining an ether linkage; R¹ is an alkylene radical having 2 to 4carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbonatoms; R² is hydrogen or a (primary amino)-alkyl group having 2 to 4carbon atoms; and x is 2 or 3; (ii) reaction products of a primaryamine-functional silane of the formula (I) with an epoxy-functionalsilane of the formula:

    A-- Si(B).sub.a (OB).sub.(3-a)                             (II)

where A is an epoxide-substituted monovalent hydrocarbon radical having4 to 12 carbon atoms; the radicals B, which can be the same ordifferent, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or1; and (iii) reaction products of a primary amine-functional silane ofthe formula (I) with an alpha, omega-dihydroxypolydimethylsiloxane oilof formula:

    HO(Si(CH.sub.3).sub.2 O).sub.y H                           (III)

in which y is 2 to 60; (B) a chlorinated polyolefin; and (C) apolydiorganosiloxane composition which is self-curable ormoisture-curable at ambient temperature; andtheroom-temperature-vulcanisable silicone rubber composition is appliedover the said primer composition.
 18. A process according to claim 17,wherein the polydiorganosiloxane (C) of the primer composition comprisesan alpha, omega-dihydroxypolydiorganosiloxane and a curing agentselected from the group consisting of ketiminoxysilane, acyloxysilaneand alkoxysilane curing agents, and the room-temperature-vulcanisablesilicone rubber composition comprises an alpha,omega-dihydroxypolydiorganosiloxane and a curing agent of the same typeas used in the primer composition.
 19. A process according to claim 17,wherein the polydiorganosiloxane (C) of the primer composition is apolydiorganosiloxane containing silicon-bonded hydroxyl groups asterminal groups and the room-temperature-vulcanisable silicone rubbercomposition comprises a polydiorganosiloxane terminated withsilicon-bonded hydrolysable groups of the same type as those in theroom-temperature-curable polydiorganosiloxane (C).